Funds are requested for a mass spectrometer system, composed of a PE Biosystems QSTAR QqTOF instrument plus a nanoliter flow HPLC and microsampler for the sample interface. This instrument system provides high sensitivity and mass accuracy with tandem mass spectrometry capabilities. It is ideally suited for proteomics applications either of genomes not yet sequenced or completed, or for biological samples that have limited availability, plus identification of posttranslational modifications. More than 20 investigators have projects ranging in focus from signal transduction, macromolecular assemblies, cancer and diabetes research, parasitic diseases, and discovery of novel peptides. Samples from some projects are limited in amount, requiring the high sensitivity features of the instrument system; whereas, other projects demand de novo sequencing at high resolution, or both high resolution and high sensitivity. The instruments will be operated and supervised by experienced mass spectrometrists and protein chemists, within an existing shared protein core facility with a record of productivity and collaborative interactions.